The use of formaldehyde for biologically disinfecting and decontaminating spaces such as hospital rooms, manufacturing areas, biological safety cabinets, laminar flow work stations, pass-throughs, animal cages and animal hoods is well known in the art. Usually the formaldehyde is generated as a gas by heating a predetermined amount of para-formaldehyde and then permitting the gaseous formaldehyde to stay in the space for a predetermined amount of contact time. For most applications, it is recommended that 0.3 grams of flake para-formaldehyde per cubic foot of space be used and that a minimum contact time of one hour be allowed. The other parameters, such as the temperature and humidity which should be maintained in the space, and a procedure for using para-formaldehyde for biological decontamination are disclosed in various publications, such as the publication by U.S. Department of Health, Education, and Welfare (National Institutes of Health), entitled "Formaldehyde Decontamination of Laminar Flow Biological Safety Cabinets", which is incorporated herein by reference.
One general procedure known in the art comprises placing a predetermined amount of para-formaldehyde flakes in an electric skillet, plugging the skillet into a timer, and then placing the skillet in the space to be decontaminated. However, to my knowledge the NIH publication does not specify any neutralizing agent or procedure for neutralizing the formaldehyde so as to permit immediate access upon the termination of the decontamination procedure. In addition, an operator should continuously watch the skillet to ensure that no problems develop. Normally this observation must be conducted from outside of the space being decontaminated and remote from the formaldehyde generator. Should power be lost during the process, and the skillet cools, upon return of the power, vital time will be lost while the skillet is heated up to the proper temperature. Consequently, the exact stage at which the power was lost and whether all of the formaldehyde has been generated are unknown.
Since the only procedure mentioned in the NIH publication for removing the formaldehyde gas is simply to ventilate the decontaminated space to an outside environment, there developed in the field the use of two skillets, side-by-side, one for generating formaldehyde, and one for generating a neutralizing agent, such as powdered ammonium carbonate. The procedure is to first energize the skillet containing the formaldehyde and then after a certain generating time to unplug that skillet and then permit the formaldehyde to stay in the space during a predetermined contact time. At the end of this contact time, an operator would then energize the skillet containing the ammonium carbonate and keep it energized for a predetermined amount of time. Then, following a certain neutralizing contact time, the space should be completely neutralized and immediate access available. The disadvantages of such a procedure are obvious and include the necessity for an operator to be present at all stages and to initiate each of these stages. However, a non-obvious disadvantage of this procedure is that the ammonium carbonate is a highly unstable substance and is readily neutralized by the hot formaldehyde gas. As a result, as soon as the formaldehyde gas is generated, part of it will become immediately neutralized by the exposed ammonium carbonate. Consequently, the amount of formaldehyde gas actually decontaminating the space, and hence the extent of the decontamination, is unknown.
Apparatus for the in situ decontamination of a space and subsequent neutralization of the space are disclosed in the U.S. patents to Decupper, U.S. Pat. No. 3,816,074 and to Anderson, U.S. Pat. No. 3,898,038, both of which are incorporated herein by reference. However, the apparatus disclosed in these patents cannot be remotely operated or inspected and should a power failure occur, the stage at which the failure occurred will be unknown. In addition, the forms of apparatus depicted in these patents are designed for use only in relatively large spaces such as hospital rooms and cannot be used for decontaminating smaller spaces such as biological safety cabinets and animal cages. The patent to Roy et al, U.S. Pat. No. 3,694,146 does depict a formaldehyde gas generator for the remote generation of formaldehyde, but the device depicted therein does not provide any means for the subsequent neutralization of the formaldehyde nor the automatic control and sequence indication of the generator.
Consequently, there is a need for a completely portable formaldehyde biological decontamination and neutralization device that is automatically controlled, can be inspected remote from the space to be decontaminated, and is completely self-contained.